The present invention relates generally to an improved biopsy needle, and more particularly to an elongated hollow biopsy needle assembly which is adapted to permit relatively simple disassembly, while maintaining a substantially air-tight cannula. Because of the ease of assembly and disassembly, the biopsy needle assembly of the present invention is particularly adapted for use in those situations where a disposable biopsy needle is indicated.
The present invention constitutes an improvement over those biopsy needle structures disclosed and claimed in U.S. Pat. Nos. 3,628,524 and 3,598,108, and my co-pending application entitled "BIOPSY NEEDLE HAVING INTEGRAL STYLET LOCKING DEVICE" executed on Aug. 16, 1979, as well as others. The present arrangement provides a biopsy needle assembly which is designed for ease of assembly and disassembly, and particularly with disposable needles. Provision is made to preserve both a closed symmetrical end surface between the hollow cannula and the stylet to provide a substantially air-tight cannula in the completed structure.
In the past, biopsy needles have been proposed and utilized which provide means for disassembly to facilitate sharpening, sterilization, or other routine operations. Other such structures have been provided which preserve the integrity of the structure, thereby making disassembly relatively difficult, if not impossible, with such structures having generally been designed to preserve the air-lock or air-tightness of the cannula. The present arrangement provides an improved biopsy needle assembly which is designed to permit disassembly of certain of the components, including replacement of certain of the components, particularly the needle structure. All of these features are achieved while preserving substantially an air-tight cannula.
Biopsy needles in accordance with the present invention include a cannula, a stylet which is arranged to be received within the cannula, a finger-gripping means to facilitate use, a coupling means for orienting the stylet within the cannula and for securing the cannula to the finger-gripping means along with means for orienting the stylet relative to the stylet head for achieving positive orientation of the stylet relative to the cannula. The cannula is preferably in the form of a uniform hollow cylindrical member which is provided, in the the preferred embodiment, with a bore which has a first circular diameter along the major portion of the length of the needle, and a significantly smaller circular diameter at the distal end. The internal configuration provides that specimens may be obtained without damage through crushing, thus preserving the spatial relationships of the cellular elements and organelles of tissue being biopsied. Additionally, the distal end of the cannula is formed so as to terminate along a plane which is disposed at an acute angle relative to the axis of the cannula.
The cannula is further provided with a generally cylindrical hub which has a bore extending therethrough, and which secures the proximal end of the cannula thereto. The bore formed in the hub forms an extension of the cannula bore, and a generally conical syringe-receiving counterbore is formed at the proximal end of the hub. Means are provided in the form of a flat or other radially disposed asymmetrical projection to preserve orientation of the cannula within the assembly.
The stylet is provided with an end which is generally symmetrical with the distal tip of the cannula, and a cap is secured to the proximal end. The cap is provided with a generally similar radially disposed asymmetrical projection to preserve orientation of the stylet with that of the cannula so as to provide the closed symmetrical end surface. In order to complete the orientation of the assembly, the finger-gripping means includes a generally centrally disposed coupling means with an inner surface having a radially disposed asymmetrical projections of the hub and stylet cap, with additional orientation features being present between the stylet and the stylet head.